1. Field of the Invention
The present invention relates to a valve assembly having utility in air distribution systems of the type generally used to air condition building structures. One of the most common types of such systems is the variable air volume wherein a central source of conditioned air is provided and distributed to various zones within the building via a network of ducts. Since the heating or cooling load requirements will vary from zone to zone, and within a particular zone depending upon factors such as solar load and current use, it is necessary that means be provided to selectively control the amount of conditioned air supplied to a particular zone in response to local demand.
In the variable air volume system, the above-noted objective is accomplished through the provision of at least one plenum chamber associated with each zone, generally located in a ceiling plenum above the zone, which includes one or more air outlets in communication with the zone. A control valve within the plenum chamber is controlled by a thermostat in the zone to supply the proper volume of conditioned air thereto so as to maintain a predetermined temperature.
The present invention is directed to a novel control valve assembly for use in an air distribution system as described above.
2. Description of the Prior Art
The most common type of control valve presently used in variable air volume systems is shown in U.S. Pat. No. 3,687,364 and comprises a plenum chamber having an inlet and outlet with a flat damper plate disposed therebetween to control flow. An actuator mounted external to the plenum chamber is linked to the damper plate and positions same in response to zeno temperature. Said actuator may be either an electric motor as shown in the referenced patent, or a pneumatic cylinder as shown in U.S. Pat. No. 3,719,321.
A more recent development in control valves of the type under consideration is disclosed in U.S. Pat. No. 3,974,859, assigned to the same assignee as the present application. This valve is characterized by a cylindrical sleeve disposed within the plenum chamber having one end thereof connected to conditioned air supply duct and including a plurality of radially extending apertures passing therethrough. A cylindrical valve member is disposed within the sleeve and mounted for movement between first and second positions so as to selectively vary air flow from the sleeve into the plenum chamber via the radial apertures. The valve member is designed in such a way that its axial ends are in communication, resulting in a balanced valve.
The present invention is directed generally to a valve of the latter type, including novel actuator structure incorporated therewith, resulting in a commercially practical valve assembly which may be powered using a variety of currently available thermostatic controls.